The Forensic Laboratory Needs Technology Working Group (FLN-TWG) summarizes the current state of three-dimensional (3D) imaging technology used in firearm and toolmark forensic analysis and provides guidance to laboratory managers who are considering the adoption of this technology.
In the past decade, the application of 3D imaging methods capable of measuring the x, y, and z coordinates of microscopic features within a toolmark has enabled the development of high-resolution digital images and measurement of the surface topographies of those microscopic features. The advancement in instrumentation used for virtual comparison microscopy facilitates the viewing of accurate representations of toolmarked surfaces and the collection and measurement of topographic data from the evidence. This makes comparisons more objective compared with conventional light microscopy comparison methods. Examinations that use virtual comparison microscopy are like light microscope examinations for fully trained firearms examiners; however, transitioning to on-screen examinations of digital images requires an adjustment period. Preparation includes learning the mechanics of the instrument and software, along with viewing the images of firearms components in a slightly different way, although the principles of the examination will not change. This adjustment period should take a few months. Staff will be required to acquire a skill set based in an understanding of instrument maintenance, conducting performance checks, validation requirements, monthly quality assurance, and quality control documentation, as well as maintaining equipment records. Depending on the instrument(s) and software packages a laboratory selects, some level of training for sample acquisition and analysis will be required. Current instruments for use in laboratories have varying types of software and hardware, requiring a determination of the best fit for a particular laboratory. The current guide discusses personnel considerations, potential funding sources, the pros and cons of investing in such technology, and considerations for implementation. Appended overview of currently available instruments